Optimal Wavefronts for Maximum Ratio Transmissions Under Path Blockage Effects

In this paper, the optimal wavefronts for maximum ratio transmission (MRT) are investigated under path blockage effects in the near-field region. To characterize the behavior of the optimal wavefronts, a new deterministic channel model is proposed in the presence of obstacles, which describes blockage effects by the variation of the electric field based on the uniform theory of diffraction (UTD). With the proposed channel model, the linear precoder designs are formulated as optimization problems to maximize the power density at the desired point under fully digital and analog array assumptions, where the amplitude and phase distributions of the solutions characterize the optimal wavefronts to achieve MRT. The optimal precoders reveal that the proposed channel modeling must be required to optimize near-field communications systems in the presence of obstacles, which, together with electromagnetic wave simulations, confirm that linear precoding with the proposed channel model achieves MRT under any blockage effect, and the optimal wavefront varies for each blockage situation.